why aren’t geothermal heat pumps not as popular anymore?

Geothermal heat pumps are actually becoming more popular as their cost falls and competing sources of heating and cooling get more expensive. There are also government grants available in many countries (including in the US as a result of the Economic Stabilization Act) that are making installation more affordable.

However, geothermal heating and cooling is an expensive up-front investment for a homeowner, and if you want to install it in an existing home the installation can be quite disruptive to the site. A vertical loop installation only requires a few bore holes going straight down, but vertical loops are the most expensive configuration. A horizontal loop requires a major dig-up of a yard, and in dense city sites a homeowner may simply not have the land for a horizontal loop (or may not want to dig up landscaped areas of their yard).

I think there are many reasons why geothermal heat pumps are not as popular as they should be – in spite of the fact that they are a cleaner source of energy than most other forms of heating and cooling, even factoring in the coal used to generate the electricity that runs them. People aren’t aware of this option for heating and cooling their homes (and even producing their hot water); they are afraid of being the first on their block to try it out; they worry about the disruption involved in installing it; they don’t realize how efficient it is; they don’t have the money for the installation (the recent economic downturn has probably put a damper on installations); or they don’t understand how to do energy payback calculations so they can’t see how quickly the system can pay for itself.